Of course Eustace knew lots of answers to this, but he didn't say anything.

The reason was that at that very moment he looked at the waves and saw that they did look very much indeed as if they were going up and down.

He had only once been in a ship(and then only as far as the Isle of Wight)and had been horribly seasick.

The look of the waves in the picture made him feel sick again. He turned rather green and tried another look.

And then all three children were staring with open mouths.

What they were seeing may be hard to believe when you read it in print, but it was almost as hard to believe when you saw it happening.

The things in the picture were moving.

It didn't look at all like a cinema either;the colours were too real and clean and out-of-doors for that.

Down went the prow of the ship into the wave and up went a great shock of spray.

And then up went the wave behind her, and her stern and her deck became visible for the first time, and then disappeared as the next wave came to meet her and her bows went up again.